Impact wrench



United States Patent 3,212,590 IMPACT WRENCH Martin D. Hoza and George A. Boyd, Houston, Tex., assignors to Reed Roller Bit Company, Houston, Tex., a corporation of Texas Filed July 29, 1963, Ser. No. 298,273 9 Claims. (Cl. 173-93) This invention relates generally to a fluid operated rotary impact tool adapted to rotate and provide impact blows to screws, nuts, bolts and the like.

It is an object of this invention to provide a new and improved portable impact tool which will deliver high impact torque for its weight and size.

Another object is to provide a new and improved, compact and lightweight impact tool which is simple in construction and easy to service.

Another object is to provide a new and improved camming device for an impact wrench.

Another object is to prevent excessive heating of portions of the tool by reducing friction and drag to improve efliciency of the tool and to provide a higher torque output.

Other objects will become apparent from the following description and accompanying drawings in which:

FIG. 1 is a longitudinal sectional view of an impact wrench showing the position of the various parts.

FIG. 2 is a view similar to FIG. 1 but with the motor and housing removed.

FIG. 3 is a pictorial view of the cam and timer elements of the tool.

Referring to the drawings, an elastic pressure fluid operated impact tool is shown comprising a housing enclosing a rotary vane type motor 11. The motor 11 has a rotor 12 having slidable vanes 13 extending between a front bearing plate 14 and the rear bearing plate 15. The rotor 12 is rotatably mounted on bearing assemblies 16 and 17. The rotor 12 has a shoulder 18 against which is disposed a thrust sleeve 19. A roller bearing assembly 20 is disposed between the thrust sleeve 19 and a thrust Washer 21. A compression spring 22 extends between the thrust washer 21 and a thrust plate 23 resting on a housing web 24 to urge the motor 11 toward the front of the tool to take up end play.

A rotatable anvil 25 is disposed in the front end of the tool, and is provided with 'a suitable bearing 26. The tool may be provided with suitable lubricant through the plug 27. The anvil 25 has a reduced end 28 which extends through the bearing 26 and from the housing 10,

and is provided with suitable driving flats 29 or the like and a locking device 30 which are adapted to rotatably drive and retain a socket (not shown). The anvil 25 has stricken jaws 31 arranged interiorly of the tool.

The rotor 12 has a bore 32 therethrough, a portion of which is splined as shown at 33. A hammer 34 has an enlarged portion 35 extending forwardly of the motor 11, and is provided with one or more striking jaws 36 arranged in confronting relation with the stricken jaws 31 of the anvil 25. The hammer 34 has a reduced splined portion 37 which registers with and telescopes within the splined portion 33 of the rotor 12. A cam element 38 i is provided in the bore 32 in axial alignment with an end 39 of the reduced, splined hammer portion 37. Abutting the end 39 of the hammer is a timer element 40 which has internal splines 41 and an axially extending portion 42. The rotor 12 has a radial bore 43 into which is disposed a roller cam assembly 44.

The cam element 38 is mounted on the extending portion 42. The timer element 40 has a tang portion 45. The forward face of the cam element 38 has a projection 46 which extends into the orbital path of the tang portion 45 to rotatably drive the timer element and to permit 3,212,590 Patented Oct. 19, 1965 relative, limited angular movement therebetween. Ball bearings 47 are provided between the cam element 38 and the timer element 40. The cam element is positroned axially on the extension 42 by means of a snap ring 48.

A cam shaft 49 extends between the anvil 25, through the motor rotor 12 and cam element 38 and through the thrust sleeve 19. The forward end of the cam shaft 49 is disposed within a bore 50 of the anvil 25. The rear end of the cam shaft 49 is provided with splines 51 which are adapted to engage with the corresponding splines 41 in the timer element 40 to provide a driving connection between the shaft 49 and the timer element 40. The cam element 38 is provided with a circular cam surface 52 that is symmetrical and which is adapted to engage with the cam roller 44 which is carried by the rotor 12.

The forward end of the cam shaft 49 is provided with a pin 53 which engages within a bore 54 of the shaft 49 and a bore 55 of the anvil 25 so that the cam shaft rotates with and is properly angularly aligned with the anvil.

A shoulder 56 is provided on the cam shaft 49, and

an internal shoulder 57 is provided on the hammer 34.

A compression spring 58 is disposed between the shoulders 56 and 57 to urge the hammer 34 toward the motor 11 and away from the anvil 25.

The housing 10 has a handle portion 59 which carries a trigger 60 which is adapted to admit pressure fluid into the tool from a suitable pressure source through the connection 61. The handle 59 has a fluid passageway 62 which directs fluid through the reversing valve 63 to the motor 12 to effect clockwise or counterclockwise rotation of the tool as desired, as is well known in the art. The fluid is exhausted through the ports 64.

The rear end of the cam shaft 49 extends through a thrust cup 65, and a pin 66 extends through the rear end of the cam shaft 49 so that the ends of the pin 66 abut internal shoulders of the thrust cup 65. The thrust cup 65 lies axially rearwardly of the thrust sleeve 19 which in turn rests against the shoulders 18 of the rotor 12. In this arrangement the camshaft 49 is prevented from moving axially to the left, .as shown in FIG. 1.

The spring 58 is precompressed and disposed between the shoulders 56 and 57 as previously described. Thus it can be seen that the hammer 34 may move axially for ward against the compression of the spring; however, the cam shaft is restrained from such axial movement by reason of the pin 66 locking it axially as just described. While the cam shaft 49 is constrained from moving axially to the left, it is adapted for rotation with the anvil 25 by means of the locking pin 53, as previously described.

Since the shaft 49 is secured to prevent axial movement thereof toward the anvil, the spring 58 does not exert an axial force on the anvil through the shaft. The anvil is thus free to rotate or float without any axial load being imposed thereon by the spring. This of course reduces the friction of the anvil by reducing the axial force against the bearing 26, and thus alleviates heat which maybe generated in the bearing and its housing during continued use of such tool. In addition, since the anvil 25 is thus isolated from the axial force of the spring, the motor may run at a higher free speed for more rapid run down of the fastener, and, because such friction is reduced, a higher torque output is afforded. Moreover, friction between the cam element 38 and the timer element 40 is reduced by the employment of ball bearings 47 therebetween.

In operation, the trigger 60 is depressed to open the valve whereupon the pressure fluid is introduced into the passageway 62 thence to the reversing valve 63 and on into the motor 11. As the motor begins to turn, the cam roller means 44 engages the cam surface 52 to rotate the cam element 38. The projection 46 in turn engages the tang portion 45 of the timer element 40 to turn the shaft 49, which is rotationally secured to the anvil 25 by means of the pin 53 to rotate and angular'ly position the jaws 31 of the anvil with respect to the jaws 36 of the hammer, and run up a work piece such as a bolt (not shown). As long as the resistance to rotation of the anvil is relatively light, the Work piece is driven as just described with the jaws 31 and 36 being held axially apart by the spring 58 during such operation, and, with an air pressure supply of about 90 p.s.i., the speed of the tool is about 7100 r.p.m.

As the work piece is tightened, the anvil resists rotation whereupon the cam roller 44 proceeds up the cam surface 52 of the cam element 38, and compresses the spring 58, to move the hammer 34 forwardly to engage the anvil 25. Before the hammer jaws 36 strike the anvil jaws 31, the cam roller 44 passes over a crest 67 .of the cam element 38 thereby momentarily freeing the cam roller 44 from operative association with the cam element 38. The inertia of the hammer 34 maintains the hammer jaws 36 in engagement with the anvil jaws 31 until the combined kinetic energy of the motor 11 and the hammer 34 is delivered to the anvil 25 and to the work piece. After such impacting, the spring 58 disengages the hammer jaws 36 from the anvil jaws 31, thus allowing the motor 11 and the hammer 34 to accelerate for the next impact. The cam surface 52 is then again engaged by the roller 44 to angularly position the hammer jaws 36 and the anvil jaws 31, and the impact operation just described is repeated. During impacting, the tool operates at approximately 1700 r.p.m. and impacts once per revolution.

During the run up of the work piece as just described, the anvil 25 is maintained tight to the work by reason of such cam engagement, thus permitting the transmission of a maximum amount of energy to the work during impact. Because the hammer 34 is telescoped within the motor 11, the motor weight is coupled directly to the hammer weight thus providing a large effective mass for impacting the anvil 25.

This invention is not limited to the embodiment shown. Various changes within the scope of the following claims will be apparent to those skilled in the art.

We claim:

1. An impact wrench comprising a housing, an elastic pressure fluid operated motor, the said housing having fluid passageways communicating with said motor, a rotatable hammer having an enlarged end and a reduced end, the said reduced end being coaxial with and telescoped within said motor, means within said motor to cause said motor to rotate said hammer and permit said hammer to reciprocate axially, the said enlarged end of said hammer having one or more striking jaws, a rotatable anvil having one or more stricken jaws confronting said striking jaws, spring means urging the hammer axially from the anvil, a timer element abutting the reduced end of said hammer, a cam element drivingly connected to said timer element, a rotatable shaft extending between the said anvil and timer element, a radially disposed cam roller carried by said motor and engaged with the said cam element, the forward end of said shaft having driving means engaged with said anvil, the said timer element having splines therein, the rearward portion of said shaft having splines drivingly engaged with said timer element splines, the said cam roller adapted to move the cam element, the timer element and hammer axially to effect engagement of the said striking and stricken jaws upon a predetermined resistance to rotation of the said anvil, the said shaft adapted to maintain a predetermined angular relation between the said anvil and timer element, the

rearward end of the said shaft extending beyond the motor and having an annular member mounted thereon, and means interposed between said motor and annular member to prevent movement of the shaft toward the anvil.

2. An impact wrench comprising a housing, an elastic pressure fluid operated motor, a rotatable hammer having an enlarged end and a reduced end, the said reduced end being coaxial with and telescoped within said motor, means within said motor to cause said motor to rotate said hammer and permit said hammer to reciprocate axially, the said enlarged end of said hammer having one or more striking jaws, a rotatable anvil having one or more stricken jaws confronting said striking jaws, spring means urging the hammer axially from the anvil, cam means disposed adjacent the reduced end of said hammer, a rotatable shaft extending between the said anvil and cam means, the forward end of said shaft having driving means engaged with said anvil, means interposed between the rearward portion of said shaft and said cam means for driving said shaft, means carried by said motor and engaged with said cam means to move said cam means and hammer to effect engagement of the said striking and stricken jaws upon a predetermined resistance to rotation of the said anvil, the said shaft adapted to main tain a predetermined angular relation between the said anvil and cam means, the rearward end of said shaft having an annular member mounted thereon, and means interposed between said motor and annular member to prevent movement of the shaft toward the anvil.

3. An impact wrench according to claim 2 wherein anti-friction bearings are disposed between said cam means and driving means for said shaft.

4. An impact wrench comprising a motor, a hammer rotatably carried by and slidable within said motor, means within said motor to cause said motor to rotate said hammer and permit said hammer to reciprocate axially, said hammer having at least one striking jaw, a rotatable anvil having at least one stricken jaw, yieldable means urging the hammer axially away from the anvil, a shaft extending through said motor and having an end engaged with said anvil for rotating same, cam means supported on said shaft and acting in opposition to said yieldable means to move the hammer to effect engagement of the hammer and anvil jaws, means carried by said motor and engaged with said cam means for moving same, means on said shaft engaged by said cam means to rotate said shaft and effect a predetermined angular relation between said hammer jaw and said anvil jaw upon operation of said motor, said shaft having an annular member mounted on the other end thereof and means interposed between said motor and annular member in coaxial relationship with said shaft to prevent axial movement of said shaft.

5. An impact wrench according to claim 4 wherein the other end of said shaft has a pin extending therethrough and a sleeve member surrounding said shaft and interposed between said motor and pin.

6. An impact wrench according to claim 4 wherein the shaft is secured in axial relationship with said anvil.

7. An impact wrench according to claim 4 wherein anti-friction bearings are disposed between the means on said shaft and said cam means.

8. An impact wrench comprising a motor, a hammer rotatably carried by and slidable Within said motor, means within said motor to cause said motor to rotate said hammer and permit said hammer to reciprocate axially, said hammer having at least one striking jaw, a rotatable anvil having at least one stricken jaw, yieldable means urging the hammer axially away from the anvil, a shaft extending through said motor and having an end engaged with said anvil for rotating same, cam means supported on said shaft and acting in opposition to said yieldable means to move the hammer to effect engagement of the hammer and anvil jaws, means carried by said motor and engaged with said cam means, means on said shaft engaged by said cam to rotate said shaft and effect a predetermined angular relation between said anvil and said cam means,

said shaft having a pin extending through the other end thereof, a cup member Supported on said shaft and engaging said pin, and a sleeve surrounding said shaft and engaging said motor and cup member whereby axial movement of the shaft is prevented.

9. An impact wrench according to claim 8 wherein the shaft is secured in axial relationship with said anvil.

6 References Cited by the Examiner UNITED STATES PATENTS 2,825,436 3/58 Amtsberg 192-305 3,070,201 12/62 Spyridakis 19230.5 3,119,456 1/63 Burnett 173--93 BROUGHTON G. DURHAM, Primary Examiner. MILTON KAUFMAN, Examiner. 

4. AN IMPACT WRENCH COMPRISING A MOTOR, A HAMMER ROTATABLY CARRIED BY AND SLIDABLY WITHIN SAID MOTOR, MEANS WITHIN SAID MOTOR TO CAUSE SAID MOTOR TO ROTATE SAID HAMMER AND PERMIT SAID HAMMER TO RECIPROCATE AXIALLY, SAID HAMMER HAVING AT LEAST ONE STRIKING JAW, A ROTATABLE ANVIL HAVING AT LEAST ONE STRICKEN JAW, YIELDABLE MEANS URGING THE HAMMER AXIALLY AWAY FROM THE ANVIL, A SHAFT EXTENDING THROUGH SAID MOTOR AND HAVING AN END ENGAGED WITH SAID ANVIL FOR ROTATING SAME, CAM MEANS SUPPORTED ON SAID SHAFT AND ACTING IN OPPOSITION TO SAID YIELDABLE MEANS TO MOVE THE HAMMER TO EFFECT ENGAGEMENT OF THE HAMMER AND ANVIL JAWS, MEANS CARRIED BY SAID MOTOR AND ENGAGED WITH SAID CAM MEANS FOR MOVING SAME, MEANS ON SAID 